Finished my first run through of the campaign on heroic difficulty last night. Overall fun experience, felt the story was good, some interesting stuff On the other hand, I'm not really sure its the 9.5 superawesome gamesites seem to proclaim. Haven't jumped into multiplayer yet, so here are my thoughts on the single player aspect. No spoilers.
I suppose the premise for Halo Reach is the idea that 'you are not alone', in the sense that this is supposedly a squad support type tactical FPS. Yes you tend to operate with some sort of support, some by 'story characters' the other members of your Spartan "Noble Team", othertimes redshirts, I mean marines/militia types that join up with you.
Lets review:
Story characters attached benefit from nigh-invulnerability. Your Spartan buddies take grenades and take shots and melee smacks by those behemoth Hunters. On the flip side, they can also be extremely frustrating, providing you with inconsistent support as they decide to hide behind things and talk alot. You can't swap out their weapons, which is a shame. This becomes especially noticeable on several 'defend objective' missions where in general its a scavenger hunt for good gear anyway, but on one mission where you have to hold a location, it seems especially out of place that literally, behind the Spartan team is a wall of grenade launchers, rocket launchers and a frickin Spartan Laser, but nope, battle rifle guy sticks with his peashooter, and shotgun guy decides its good to hold onto even though that means he can't engage 80 percent of the incoming foes until they're in his face.
Also, while I understand the need for balance, so that squadmate NPCs don't killsteal and do everything for you, at least on Heroic difficulty it appears something of the opposite, you'll have to kill 90-95% of opposition, (unless the NPC is riding shotgun on the gatling gun or other semi-fixed emplacement), as your NPC Spartans are inconsistent help.
Redshirts. Through the course of the game, you can pick up temporary companions. Marines or militia-men in your mission areas. They have a benefit of infinite ammo, so hand them a weapon with only 1 shot left and they're good to go. On the other hand, they're fragile, and generally not very bright. There's no 'squad command' functions ala Republic Commando or Brothers in Arms, so the redshirts function on their own AI, which tends to go like this, "Ohh hey great we've got a Spartan with us! We're awesome! Chaaaaarge! <3 guys slaughtered by 1 grunt>" They have a tendency to run ahead to the next checkpoint, even before you manage to reach them to give them a new weapon.
As for redshirts and weapons, I'd have to say No to Sniper weapons, the redshirts AI simply don't have the means to benefit that greatly from the range advantage, so they'll be using it at way too close quarters. On the other hand, giving the redshirts sniper rifles to HOLD is a great idea, as they can potentially become a mobile sniper-rifle armory for you to use. If you take back a weapon you gave to an NPC, it has the same ammo count as when you gave it, even if they've been using it. Another thing I noticed, on levels you actually come across something decently awesome like a Rocket Launcher or Focus Rifle or concussion rifle, you can give them to redshirts, but I can think of only 2 times where they got to use it, other times you cross a story checkpoint and suddenly the redshirts portion of the follow-mission is done, and they'll stand guard or disappear and never actually engage again. Its like finding a BFG after you've finished the chapter's boss fight. Gee thanks.
Though in two instances I managed to give a rocket launcher to a redshirt and they 1)stayed with me for a decent long time 2)actually got to use the launcher to good effect. I've yet to actually see a redshirt get a chance to use a focus rifle (beam weapon) or concussion rifle after I gave it to them as surprise, the mission was soon finished.
Halo Reach also provides the player a chance to swap out armor abilities and buy armor costume pieces that doll up your Spartan Barbie and appears in the cutscenes, making your individual pink neon Spartan possible to see during the campaign movies.
The good (armor kits): Interesting abilities. Instead of one use power-ups like the previous games, you can fit in the ability to sprint, or cloak, or temporary invulnerability, or even jump-jet. Making a holographic decoy is also rather useful once you get the hang of it.
The not so good: Every mission default swaps you back with Sprint. I guess this is a game balance issue, as in some missions actually having stealth or jumppacks (even though they were abundant and required the mission before) would make things too easy. Still, it feels rail-roady. Don't get me wrong, Sprint is very useful, from closing for melee or making it easier to hijack that wraith tank. Just you'll often run into missions where midway through you realize, "Oh, obviously they won't give me stealth at all on this map, cause that'd actually let me approach this without guns a blazin. On that note, same thing for weapons. Every mission default swaps you to whatever the mission wants you to start with. In some cases it makes sense, other cases its like "Oh, pistol and battle rifle again huh?" Maybe battle rifle is useful on difficulties lower than Heroic, but it just doesn't cut it on harder difficulties.
The good and the not so good(armor customization): You can have your pink vomit Spartan show up in cutscenes and you can pay for costume upgrades, new helmets, chest, shoulders, arms, knee pads, whatever. Each has their own new little blurb description. Unfortunately, none provide any real stat changes. This is where I think they dropped the ball. Little things that could be modified, like if I wear the grenadier mod, maybe I could get another grenade to hold rather than the 2/2 limit. Or the ability to hold more ammo, or etc etc. Basically its just a barbie-doll application.
Badguy AI? Pretty brutal, almost to the point of cheating at times. If you don't keep your eye on the Elites, or the jumppack types, they WILL kick your ass.